That's because as you grow up, most people can see that Santa Claus is fake. You're clinging to myths and children's stories as an adult without the proper critical thinking like an adult should. It's absurd to think that some invisible stone cutter made the tablets, and the only real conclusion you can come to is that Moses was a liar and made them himself, IF that story actually even happened.
I learned the truth about Santa when I was seven. I was thrilled. Until then I didn't realize just how good adults were at playing. Couldn't wait to grow up and play Santa myself.
This, I think, is the difference between us. The reality you saw was "Fake Santa". The reality I saw parents at play with their children. Great game, too.
I see you are still clinging to the child's belief of literal scripture. Did you never study the original Hebrew? Did you miss the English lessons on figurative speech?
Moses probably had a realization (that most people have at some time in their life) that the Ten Commandments had to come from elsewhere; that he, as a man, hadn't given these issues much thought. Yet, suddenly, they were in his mind and heart. As an atheist, you might say, "They had been in his subconscious and finally emerged." Okay. That's what some believe.
People of faith see it differently. Those who see figurative speech in the story, relate it to the Spirit of God or the Holy Spirit, because that same language is used elsewhere in the Bible regarding the Holy Spirit. Moses felt he was overcome by the spirit of God, and the Commandments came from that Spirit--not from anything in his own mind.
As for those who take the finger of God literally: This is a true childlike faith, and Christ said blessed are they who have the faith of a child. I may doubt their knowledge of language and science--but I never doubt their faith. In the end, faith is more vital than either of the others.